1. Field of the Invention
This invention concerns a thin layer magnetic head used for recording and reproduction, for example, in a magnetic disk storage apparatus and a magnetic disk storage apparatus mounting the magnetic head.
2. Description of the Background
In a magnetic disk storage apparatus, data on the recording media is read and written by a magnetic head. In order to increase the recording capacity per unit area of the magnetic disk, it is necessary to increase the area recording density. However, the area recording density of existing in-plane recording systems can not be increased as the length of bits to be recorded is decreased because of thermal fluctuation in the magnetization of the media.
A perpendicular recording system which records magnetization signals in a direction perpendicular to a medium is adapted to address this problem. In the perpendicular recording system, a magnetoresistive head (“MR head”) and a giant magnetoresistive head (“GMR head”) with a larger read output than non-perpendicular systems can be used for reading. However, a single pole head must to be used for the writing head in these systems. With perpendicular recording, it may be necessary to improve the track density and the linear recording density in order to improve the recording density. To improve the track density, the track width of the magnetic head is decreased and formed with higher accuracy.
In a perpendicular recording system, the shape of the main pole of the single pole type recording head has a significant effect on the magnetization pattern of the media. Specifically, the shape of the upper end face of the main pole, which is the end face of the main pole on the side opposite to the MR head (on the trailing side), greatly affects the shape of the magnetization pattern of the media. For example, JP-10-320720/1998 discloses the structure of a single pole type head having a main pole of a trapezoidal shape flattened at the upper end face and wider on the side of the MR head.
However, in the description in JP-10-320720/1998, a description is made of side recording tracks defined by the slope on both sides of the trapezoidal shape. These side recording tracks reduce cross talk with adjacent recording tracks, however, they hinder the improvement of the track density which therefore hinders any improvement in the area recording density. In such a magnetic disk storage apparatus, a skew angle is formed when the magnetic head scans from the inner circumference to the outer circumference of a disk, in which the trapezoidal pole shape erases signals on adjacent tracks. JP-10-320720/1998 has no specific descriptions about the pole forming method.
By using a polishing method, the upper surface of the main pole (second pole) can be flattened. However, when a polishing method such as chemical mechanical polishing (CMP) is used, it is difficult to control the layer thickness which hinders the accuracy of the layer thickness. The thickness may vary by as much as about ±0.5 μm. This inaccuracy scatters the layer thickness of the main pole, thereby causing scattering in the intensity of the magnetic field from the main pole. Accordingly, it is preferred to adopt a flattening method for the upper surface of the main pole having improved controllability (accuracy) for the layer thickness.
In view of the above, the present invention preferably provides a magnetic head for perpendicular recording having a main pole of a shape with no side recording which does not erase signals on adjacent tracks caused by a skew angle. The invention also includes a manufacturing method of the magnetic head and a magnetic disk storage apparatus mounting the magnetic head for perpendicular recording.